According to the Nestjs docs:
But first (if you use TypeScript), we need to determine the DTO (Data Transfer
Object) schema. A DTO is an object that defines how the data will be
sent over the network. We could determine the DTO schema by using
TypeScript interfaces, or by simple classes. Interestingly, we
recommend using classes here. Why? Classes are part of the JavaScript
ES6 standard, and therefore they are preserved as real entities in the
compiled JavaScript. On the other hand, since TypeScript interfaces
are removed during the transpilation, Nest can’t refer to them at
runtime. This is important because features such as Pipes enable
additional possibilities when they have access to the metatype of the
variable at runtime.